The present invention relates a high-purity titanium ingot, a manufacturing method therefore, and a titanium sputtering target. The high-purity titanium ingot or target contains a nonmetallic element, has a uniform structure with low intra- and inter-ingot variations or intra- and inter-target variations, and has high strength. Throughout the specification, the impurity concentration is expressed as ppm by mass (mass ppm).
In recent years, various electronic instruments have been developed originated from a significant progress of semiconductors, and improvements in performance of the instruments and development of novel instruments are being performed daily and hourly.
In such a circumstance, there is a tendency that electronic devices and instruments are further reduced in size and are increased in degree of integration. A large number of thin films are formed in various steps of manufacturing these instruments, and titanium is also utilized, because of the specific metallic properties thereof, in formation of thin films of many electronic instruments as, for example, titanium or its alloy films, titanium silicide films, or titanium nitride films.
In general, films of titanium, its alloy, titanium silicide, titanium nitride or the like as described above can be formed by physical vapor deposition such as sputtering and vacuum vapor deposition. In particular, high-purity titanium is used as a wiring material of semiconductors.
Wiring of a semiconductor is usually formed by sputtering. The sputtering is a method of allowing positive ions such as Ar+ to physically collide with an ingot disposed on the cathode to release metal atoms constituting the ingot by the collision energy. A nitride can be formed by sputtering using titanium or its alloy as an ingot in an atmosphere of a gas mixture of argon gas and nitrogen.
Recently, there is a demand for high-rate sputtering (high-power sputtering) in order to increase the production efficiency. In such sputtering, cracking or breaking of the ingot is apt to occur, and this disadvantageously prevents stable sputtering. It is therefore important that titanium itself has high strength. Titanium targets and methods of producing titanium targets are described in, for example, Patent Documents 1 to 8. Methods of producing high-purity titanium are described in, for example, Patent Documents 9 to 11.    Patent Document 1: International Publication No. WO01/038598    Patent Document 2: JP 2001-509548 A    Patent Document 3: JP H09-25565 A    Patent Document 4: JP 2000-219922 A    Patent Document 5: JP 2010-235998 A    Patent Document 6: JP H10-140339 A    Patent Document 7: Japanese Patent No. 3621582    Patent Document 8: JP 2004-518814 A    Patent Document 9: JP H08-225980 A    Patent Document 10: JP H09-25522 A    Patent Document 11: JP 2000-204494 A